Rob,
I've done a number of them, and can attest that Alton Brown's "reverse sear" method for rib roast is outstanding. Low and slow until 128 or so, rest covered until 135 or so, then sear at high heat for 15 minutes. I'll be doing just that and enjoying a great Christmas dinner with sweet potatoes and au jus. Best wishes on however you do yours. Merry Christmas.